JPH0626183B2 - Valve for CVD equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a valve of a CVD apparatus used for manufacturing a semiconductor or the like.

(Prior Art) Conventionally, a CVD (Chemical Vapor Deposition) method for forming a thin film on a substrate provided in a film forming chamber by introducing a plurality of kinds of gases into a vacuum film forming chamber is known, for example, for semiconductors. Used in the manufacture of. The outline of the apparatus used for this is as shown in the first diagram, in which a substrate c is placed on a rotary table b in a film forming chamber a which is evacuated to a vacuum by a vacuum pump, and, for example, H through a valve d. _{2, A} S _H 3, TM
The reaction gas such as Ga can be introduced into the film forming chamber a. The specific structure of the valve d is, as shown in FIG. 2, provided with a bellows f operated by air pressure introduced from a port e and a valve body h integrated with a connecting rod g connected to the bellows f. When h moves up and down, the flow passages j and k formed in the valve case i are opened and closed.

(Problems to be Solved by the Invention) A thin film formed by the CVD method on the substrate c is a super-low
With the development of SI technology and compound semiconductor technology, thin films formed by rapid growth have been required. For example, in a quantum well device, it is necessary to form an active region of 20 to 30 angstroms in the depth direction, and composition control for each atomic layer (to 3 angstrom) is required. These requirements are
It will become more and more severe with the development of quantum wave devices in the future.

The start of growth of the thin film is controlled by opening and closing the valve d, and the volume from the seat portion of the valve d to the film forming chamber a is a major factor for obtaining rapid film growth. When the valve having the structure shown in the second diagram is used, the volume from the valve seat portion to the film forming chamber a becomes a dead volume, and when the valve is opened, the dead volume becomes a gas reservoir, and then the valve is opened. Sometimes the accumulated gas was pushed out first, gradually increasing the gas concentration,
The thin film is formed on the substrate c only with a slow profile.

An object of the present invention is to provide a valve that enables a thin and abrupt thin film to be formed on a substrate in a CVD apparatus.

(Means for Solving Problems) In the present invention, in a valve for introducing a reaction gas into a vacuum film forming chamber provided with a substrate on which a thin film is formed by a thermochemical reaction, the valve case of the valve is Forming a long cylindrical portion to be inserted into the film forming chamber and opening an outlet at the tip of the long cylindrical portion,
By providing an opening and closing poppet which is seated in the outlet in the long tubular portion, the above-mentioned problem is solved.

(Operation) When the reaction gas is introduced into the vacuum film formation chamber, the reaction gas comes into contact with the heated substrate in the film formation chamber to cause a thermochemical reaction,
A thin film of that component is formed on the substrate. The reaction gas is introduced into the film forming chamber through a valve, and the valve is attached by inserting the long cylindrical portion formed in the casing directly into the film forming chamber and flowing at the tip of the long cylindrical portion. Since it is configured to form the outlet and seat the poppet there, when the poppet closes the outlet, there is no place where reaction gas accumulates from the poppet to the film forming chamber, Therefore, when the poppet is opened next time, the concentration of the reaction gas in the film forming chamber rapidly increases, and a thin film can be formed rapidly on the substrate.

(Embodiment) An embodiment of the present invention will be described with reference to FIG.

In the figure, reference numeral (1) indicates a vacuum film forming chamber in which a substrate is provided, and (2) indicates a valve for introducing a reaction gas into the film forming chamber (1). The valve (2) is provided with a piston (5) and a piston rod (6) which move against the spring (4) by the air pressure from the air pressure introduction port (3) in the valve case (7). The valve case (7) in front of the rod (6) is formed in the long tube portion (8), and the long tube portion (8) is inserted into the film forming chamber (1) to surround the valve case (7). The flange (19) was fixed to the film forming chamber (1). (9) is a circular outlet formed at the tip of the long tubular portion (8) so that the center of the piston rod (6) coincides with the axis, and (10) is seated at the outlet (9). An opening and closing poppet, and (11) is a connecting rod for connecting the poppet (10) to the piston rod (6).

Further, (12) is a sealing material provided on the outer periphery of the intermediate portion of the connecting rod (11) in contact with the inner wall of the long tubular portion (8), and (13) is a land portion formed by enlarging the connecting rod (11). , (14) are flow holes formed in the connecting rod (11), one end of which is connected to the reaction gas inlet (15) on the side of the valve case (7) and the long tubular portion (8). ) Between
It was opened in (16) and the other end was opened in the land (13). (17) is the valve seat, the extension of which is the land
The communication hole (14) which is fitted into (13) and opens therein is closed. The opening area of the flow hole (14) changes depending on the distance that the land (13) comes out of the valve seat (17), and the flow rate of the reaction gas is controlled by this change. The land part (13)
Even if the valve seat (17) and the valve seat (17) are fitted together, a slight gap is created between the two and the valve seat (17) is not fully closed or suddenly opened. Poppet (1
0) is provided. (18) is a connection port that can be opened and closed arbitrarily.

When the air pressure in the air pressure introduction port (3) is low, the piston rod (6) is pushed down by the elastic force of the spring (4) as shown in Fig. 3, and is attached to the piston rod (6) via the connecting rod (11). Poppet (1
Since (0) is seated on the outflow port (9), the passage from the reaction gas inflow port (15) into the film forming chamber (1) is closed.

Increase the air pressure in the air pressure inlet port (3)
(5) is pushed up against the spring (4), and with this
(11) and poppet (10) also move upward to open the outlet (9) and the land (13) together with the sealing material (12) to the valve seat.
Since it separates upwards from (17), the film forming chamber (1) from the reaction gas inlet (15) through the passage (16), the flow hole (14) and the outlet (9)
A reaction gas flows into the chamber, and a thin film is formed on the substrate by a thermochemical reaction caused by contact between the heated substrate in the film formation chamber (1) and the reaction gas.

The valve (2) has a long tube portion (8) in its valve case (7), and a poppet (10) is seated on an outlet (9) formed at the tip of the long tube portion (8). Therefore, by installing the valve (2) with the long tubular part (8) inserted directly into the film forming chamber (1), the reaction between the poppet (10) and the film forming chamber (1) can be prevented. It is possible to reduce dead volume in which gas accumulates. Therefore, when the valve (2) is opened, the film forming chamber
In (1), the reaction gas concentration rapidly increases, and a thin film can be rapidly formed on the substrate. Further, since the long tube portion (8) is included, the entire valve (2) can be assembled as a single unit, and the valve (2) can be directly attached to and detached from the film forming chamber (1), so that mounting and replacement can be performed. It will be easier.

In a conventional CVD apparatus using a valve shown in FIG. 2, an n-type dopant is introduced to a depth of 4 μm to 3 μm to form an n-type doping layer on a substrate, and then a non-doped GaAs is used.
The doping profile when the valve is controlled to open and close so as to form a layer of 3 μm has a gradual increase in gas concentration as shown by the curve A in FIG. 4. However, when the valve of the present invention is used, the curve in FIG. As shown by B, the doping profile was such that the gas concentration rapidly increased.

(Effects of the Invention) As described above, according to the present invention, a valve for introducing a reaction gas into a film forming chamber of a CVD apparatus is provided with a long tubular portion to form a gas outlet, and the outlet is provided at the outlet. Since the poppet for opening and closing is seated, the dead volume in which the reaction gas accumulates between the valve and the film forming chamber can be significantly reduced by inserting the long tube into the film forming chamber and attaching the valve. It becomes possible to rapidly increase the reaction gas concentration in the film forming chamber to form a thin film on the substrate rapidly.
It is advantageous for the manufacture of compound semiconductors and valve mounting.
There is an effect that it can be easily exchanged.

[Brief description of drawings]

FIG. 1 is a diagram of a conventional CVD apparatus, FIG. 2 is a specific cross-sectional view of an essential part of FIG. 1, FIG. 3 is a cutaway side view of an embodiment of the present invention, and FIG. It is a diagram showing. (1) …… Deposition chamber, (2) …… Valve (7) …… Valve case, (8) …… Long tube (9) …… Outlet, (10) …… Poppet

Claims (1)

[Claims] 1. In a valve for introducing a reaction gas into a vacuum film forming chamber provided with a substrate on which a thin film is formed by a thermochemical reaction, a long cylinder inserted into the film forming chamber in a valve case of the valve. To form an opening at the tip of the long tubular portion,
A valve for a CVD apparatus, wherein an opening and closing poppet that is seated on the outlet is provided in the long tubular portion.